Various types of instruments for inserting intervertebral disc prostheses are known, such as those disclosed in the French patent application FR0405899000 filed by the applicant. These instruments only allow insertion by anterior access, along the antero-posterior axis of the prosthesis. Preparation of the vertebrae between which the prosthesis is to be implanted by this type of instrumentation therefore requires opening the tissue covering these vertebrae and pushing aside the blood vessels on the anterior face of the spinal column, which generates a risk for the patient.
The embodiments disclosed herein provide instrumentation and methods that allow insertion of a prosthesis between the vertebrae, laterally or obliquely, while appropriately positioning the prosthesis in relation to the sagittal plane and the coronal plane.
Embodiments of instrumentation for the insertion of intervertebral disc prosthesis between vertebrae in accordance with the present invention comprise a guide and at least one separator. In preferred embodiments, the guide has at least two lateral faces, at least one upper plate, at least one lower plate, at least one retainer, a cage defining an insertion axis for the intervertebral disc prosthesis and having open posterior and anterior faces, and an angle adjuster adapted to adjust the angle formed by the insertion axis and an antero-posterior median sagittal axis of the vertebrae. The separators are sized to maintain a gap between the upper vertebra and the lower vertebra that is sufficient for insertion of the intervertebral disc prosthesis through the guide into the intervertebral space. For the disclosed embodiments, during the insertion of the intervertebral disc prosthesis the upper plate is disposed proximal to a plane substantially coincident with the lower surface of the upper vertebra, and the lower plate is disposed proximal to a plane substantially coincident with the upper surface of the lower vertebra. The upper plate and the lower plate are separated by a distance approximately equal to the height of the intervertebral disc prosthesis. The angle adjuster is adapted to position the guide opposite the intervertebral space between the upper vertebra and the lower vertebra and to adjust an angle formed by the insertion axis and an antero-posterior median sagittal axis defined by the intersection of a midline, substantially vertical, sagittal plane and a transverse, substantially horizontal, plane of the spinal column.
According to another feature in an embodiment, the angle adjuster comprises at least one sighting device configured for visual adjustment of the angle between the insertion axis and the antero-posterior median sagittal axis.
According to another feature in an embodiment, the angle adjuster comprises a sighting device configured for operation with at least one pin implanted into at least one of the upper vertebra and the lower vertebra and approximately oriented with the antero-posterior median sagittal axis of said vertebra to align said sighting device with the antero-posterior median sagittal axis.
According to another feature in an embodiment, the instrumentation further comprises:
at least one pin for implantation into at least one of the upper vertebra and the lower vertebra in approximate orientation with the antero-posterior median sagittal axis of said vertebra;
at least one offset adjuster adjustably linking the angle adjuster to the at least one pin.
According to another feature in an embodiment, the instrumentation further comprises:
at least one contact adjuster disposed approximately parallel to the insertion axis;
a coupling between the at least one contact adjuster and the angle adjuster allowing movement of the angle adjuster with respect to the at least one contact adjuster;
a connector configured to move along the longitudinal axis of the pin and to connect the at least one offset adjuster to the at least one pin.
According to another feature in an embodiment, the at least one pin comprises a sharp point.
According to another feature in an embodiment, the angle adjuster comprises at least one adjustment gauge indicating at least one parameter concerning the position of the guide relative to the vertebrae.
According to another feature in an embodiment, the adjustment gauge comprises a lateral offset gauge comprising a pointer pointing to graduations indicating the lateral offset of the guide from the antero-posterior median sagittal axis of the vertebrae.
According to another feature in an embodiment, the adjustment gauge comprises an angle gauge comprising a pointer pointing to radial graduations indicating the angle between the insertion axis of the intervertebral disc prosthesis and the antero-posterior median sagittal axis of the vertebrae.
According to another feature in an embodiment, the instrumentation further comprises a tightener that selectively allows or prevents rotation of the angle adjuster with respect to the guide, thereby permitting adjustment and fixation of the angle between the insertion axis of the intervertebral disc prosthesis and the antero-posterior median sagittal axis.
According to another feature in an embodiment, the at least one retainer comprises at least one groove permitting the at least one separator to slide within the groove.
According to another feature in an embodiment, the at least one retainer comprises at least one shaft providing at least one axis of rotation for the at least one separator.
According to another feature in an embodiment, the guide further comprises a stop limiting the rotation of the at least one separator about the at least one axis of rotation.
According to another feature in an embodiment, the rotation of an at least one separator is limited by an adjustable stop enabling to set the extent to which the rotation is limited.
According to another feature in an embodiment, the guide comprises at least one channel oriented substantially parallel to the insertion axis of the intervertebral disc prosthesis and configured to guide at least one part protruding from at least one surface of the intervertebral disc prosthesis.
According to another feature in an embodiment, the insertion axis of the intervertebral disc prosthesis through the guide is oriented approximately parallel to a longitudinal centerline of the guide passing through the open anterior and posterior faces of the cage.
According to another feature in an embodiment, the insertion axis of the intervertebral disc prosthesis through the guide is not oriented approximately parallel to a longitudinal centerline of the guide passing through the open anterior and posterior faces of the cage.
According to another feature in an embodiment, the instrumentation further comprises at least one chisel having at least one blade and suitable shape and dimension for engagement with the guide and for cutting at least one notch in a vertebra.
According to another feature in an embodiment, the chisel comprises a shaft, a handle at the end of the shaft opposite the at least one blade, and an adjustable stop limiting the travel of the chisel inside the guide.
According to another feature in an embodiment, the chisel comprises two blades and a spacer of suitable dimension to separate the blades by a distance approximately equal to the height of the intervertebral space.
According to another feature in an embodiment, the instrumentation further comprises an impactor having a shaft, a handle at one end of the shaft for manipulating the impactor, and at the other end of the shaft a pusher having shape and dimensions substantially conforming to at least one edge of the intervertebral disc prosthesis contacted by the pusher during use.
According to another feature in an embodiment, the impactor has an adjustable stop limiting the travel of the impactor inside the guide.
According to another feature in an embodiment, the instrumentation further comprises a holder for the intervertebral disc prosthesis and wherein the guide comprises a recess providing clearance for holder for the intervertebral disc prosthesis sufficient to position the intervertebral disc prosthesis into the guide.
According to another feature in an embodiment, the instrumentation further comprises a holder for the guide engaging at least two notches of the guide.
According to another feature in an embodiment, the holder for the guide is configured to engage the at least two notches of the guide without interfering with engagement of a recess of the guide by tools for accessing the intervertebral space or by the holder for the intervertebral disc prosthesis.
Methods for inserting intervertebral disc prostheses between two vertebrae are also provided.
General steps for preparing the vertebral site for insertion of an intervertebral disc prosthesis between two vertebrae are known, and are not an aspect of the inventive method disclosed herein. In general, such preparatory steps comprise removal of the natural biological intervertebral disc, clearing the intervertebral space, and maintaining a gap between the upper vertebra and lower vertebra with a known instrument.
Methods for inserting an intervertebral disc prosthesis in accordance with the present invention can be performed using instrumentation comprising at least one pin and a guide having at least one upper plate, at least one lower plate, a cage defining an insertion axis for the intervertebral disc prosthesis and having open posterior and anterior faces, and an angle adjuster. In a preferred embodiment, a method according the present invention comprises:                implanting at least one pin in the median sagittal axis of one of the two vertebrae;        measuring the dimensions of the intervertebral space;        choosing the intervertebral disc prosthesis to be implanted;        choosing the guide to be used;        adjusting the angle adjuster based on an antero-posterior median sagittal axis of the spinal column, defined by the intersection of a midline, substantially vertical, sagittal plane and a transverse, substantially horizontal, plane of the spinal column, on the dimensions of the intervertebral space and on the obstacles to access to the intervertebral space, in order to set a desired angle between the insertion axis for the intervertebral disc prosthesis and the antero-posterior median sagittal axis;        positioning the guide adjacent to the intervertebral space at the desired angle;        inserting the intervertebral disc prosthesis into the guide through the open posterior face of the cage; and        inserting the intervertebral disc prosthesis into the intervertebral space through the open anterior face of the cage.        
According to another feature in an embodiment, the method further comprises a step of adjusting an offset adjuster for setting a lateral offset of the guide relative to the antero-posterior median sagittal axis.
According to another feature in an embodiment, the step of inserting the intervertebral disc prosthesis into the intervertebral space is performed using an impactor comprising a shaft and an adjustable stop, said step further comprising adjustment of the stop and the application of a thrust to the impactor.
According to another feature in an embodiment, the step of adjusting the angle adjuster is performed using a sighting device for aligning the guide with the antero-posterior median sagittal axis, said step further comprising placement of the sighting device in contact with the at least one pin.
According to another feature in an embodiment, the method further comprises a step of adjusting an offset adjuster of adjustable length connecting the angle adjuster of the guide to a connector connected to the pin, this adjusting step being implemented thanks to the measurements of the intervertebral space.
According to another feature in an embodiment, the step of positioning the guide adjacent to the intervertebral space further comprises translation of the guide along an axis substantially parallel to the antero-posterior median sagittal axis until the guide is proximal to the vertebrae.
According to another feature in an embodiment, the method further comprises the insertion of one or more separators into the intervertebral space.
According to another feature in an embodiment, the method further comprises the engagement of at least one of the one or more separators with at least one retainer of the guide.
According to another feature in an embodiment, the step of positioning the guide is performed with a holder for the guide.
According to another feature in an embodiment, the step of inserting the intervertebral disc prosthesis into the guide is performed with a holder for the intervertebral disc prosthesis, the guide comprising a recess providing clearance sufficient for the holder for the intervertebral disc prosthesis to position the intervertebral disc prosthesis into the guide.
According to another feature in an embodiment, the step of positioning the guide is performed with a holder for the guide configured to engage at least two notches of the guide to provide clearance for tools for accessing the intervertebral space.
According to another feature in an embodiment, the method further comprises, before inserting the intervertebral disc prosthesis into the intervertebral space, the step of preparing the intervertebral space using a chisel having at least one blade, an adjustable stop and suitable shape and dimension for engagement with the guide and for cutting at least one notch in at least one vertebra.
According to another feature in an embodiment, the method further comprises the step of clearing the intervertebral space of the bone debris generated by cutting the notch.
According to another feature in an embodiment, the method further comprises a step of removing the guide, the one or more separators, and the at least one pin after the step of inserting the intervertebral disc intervertebral disc prosthesis into the intervertebral space.
Other features and advantages of the invention will become clearer upon reading the following description of various embodiments with reference to the attached drawings.